This invention relates to frequency multiplying devices in general and more particularly to a tapped delay line with an exclusive OR tree connected thereto to generate a harmonic square wave type of output signal from a basic clock signal. Frequency multiplying circuits have been in use for a long time, but have lacked precision in the multiplied output where some pulses might be generated with a different width to resynchronize the output with input transitions as in TV deflection circuits wherein a free running multivibrator is triggered by a synchronizing signal. Another known frequency doubler uses a non-tapped delay line and a single exclusive OR type circuit to generate a double frequency square wave type signal. This frequency doubler cannot be extended to higher frequency multiples of the input clock frequency.